THE NATURE OF EXTREME EMISSION LINE GALAXIES AT z = 1–2: KINEMATICS AND METALLICITIES FROM NEAR-INFRARED SPECTROSCOPY
THE NATURE OF EXTREME EMISSION LINE GALAXIES AT z = 1–2: KINEMATICS AND METALLICITIES FROM NEAR-INFRARED SPECTROSCOPY
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DOI：
10.1088/0004-637x/791/1/17
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发表时间：
2014-06
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影响因子：
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通讯作者：
M. Maseda;A. van der Wel;H. Rix;E. da Cunha;C. Pacifici;I. Momcheva;G. Brammer;S. Meidt;M. Franx;P. V. van Dokkum;M. Fumagalli;E. Bell;H. Ferguson;N. Förster-Schreiber;A. Koekemoer;D. Koo;B. Lundgren;D. Marchesini;E. Nelson;S. Patel;R. Skelton;A. Straughn;J. Trump;K. Whitaker
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作者：
M. Maseda;A. van der Wel;H. Rix;E. da Cunha;C. Pacifici;I. Momcheva;G. Brammer;S. Meidt;M. Franx;P. V. van Dokkum;M. Fumagalli;E. Bell;H. Ferguson;N. Förster-Schreiber;A. Koekemoer;D. Koo;B. Lundgren;D. Marchesini;E. Nelson;S. Patel;R. Skelton;A. Straughn;J. Trump;K. Whitaker
我们现在样品的近红外光谱22极端的发射谱线星系红移1.3 < z < 2.3,证实这些低质量(M⋆= 108 - 109☉)星系经历强烈的亮光集(M⋆/ SFR∼10 - 100最高产量研究)。利用3D-HST巡天的近红外格栅光谱，通过[O iii]或Hα发射谱线通量和等效宽度选择样品。利用LBT/LUCI和VLT/X-SHOOTER获得高分辨率近红外光谱。[O iii]/Hβ线比较高（≥5），[N ii]/Hα线比明显小于1，表明其气相金属丰度较低。我们能够使用各种强谱线方法确定七个天体的气相金属丰度，其值范围在0.05-0.30 Z☉，中位数为0.15 Z☉；对于其中的三个，我们检测到[O iii] λ4363，这允许对金属丰度的直接限制。从星云发射线测量的速度色散通常为~ 50 km s−1。结合观测到的恒星形成活动，Jeans和Toomre稳定性标准暗示气体的比例一定很大（fgas≥2/3），这与我们的动力学和恒星质量估计之间的差异是一致的。隐含的气体耗尽时间尺度（几百Myr）比推断的质量加权年龄（~ 50 Myr）要长得多，这进一步支持了低质量星系中大多数恒星形成于短而强烈的恒星形成爆发的新图景。
We present near-infrared spectroscopy of a sample of 22 Extreme Emission Line Galaxies at redshifts 1.3 < z < 2.3, confirming that these are low-mass (M⋆ = 108–109 M☉) galaxies undergoing intense starburst episodes (M⋆/SFR ∼ 10–100 Myr). The sample is selected by [O iii] or Hα emission line flux and equivalent width using near-infrared grism spectroscopy from the 3D-HST survey. High-resolution NIR spectroscopy is obtained with LBT/LUCI and VLT/X-SHOOTER. The [O iii]/Hβ line ratio is high (≳ 5) and [N ii]/Hα is always significantly below unity, which suggests a low gas-phase metallicity. We are able to determine gas-phase metallicities for seven of our objects using various strong-line methods, with values in the range 0.05–0.30 Z☉ and with a median of 0.15 Z☉; for three of these objects we detect [O iii] λ4363, which allows for a direct constraint on the metallicity. The velocity dispersion, as measured from the nebular emission lines, is typically ∼50 km s−1. Combined with the observed star-forming activity, the Jeans and Toomre stability criteria imply that the gas fraction must be large (fgas ≳ 2/3), consistent with the difference between our dynamical and stellar mass estimates. The implied gas depletion timescale (several hundred Myr) is substantially longer than the inferred mass-weighted ages (∼50 Myr), which further supports the emerging picture that most stars in low-mass galaxies form in short, intense bursts of star formation.